Modular vertex structure

ABSTRACT

1. A POLYHEDRAL STRUCTURE HAVING A PLURALITY OF VERTICES AND A PLURALITY OF EDGES MEETING AT EACH OF THE VERTICES AND DEFINING THE FACES OF THE POLYHEDRAL STRUCTURE COMPRISING: A PLURALITY OF SUPPORT FRAME MEMBERS DEFINING THE EDGES WHICH DEFINE AT LEAST CERTAIN FACES OF THE POLYHEDRAL STRUCTURE, EACH OF SAID SUPPORT FRAME MEMBERS HAVING AT LEAST ONE LEG MEMBER OF A PAIR OF LEG MEMBERS EXTENDING AT LEAST PART WAY ALONG EDGES DEFINING SUCH FACES AND AT LEAST ONE CURVED PORTION DEFINING AN ARC OF A SUBSTANTIALLY CIRCULAR AREA CENTERED IN THE FACE OF THE POLYHEDRAL STRUCTURE DEFINED BY SUCH EDGES, THE PLURALITY OF SUPPORT FRAME MEMBERS AT EACH FACE JOINED TOGETHER WITH THE CURVED PORTIONS THEREOF COMPLETELY SURROUNDING SAID SUBSTANTIALLY CIRCULAR AREA THEREOF, AT LEAST A PAIR OF SUBSTANTIALLY CIRCULAR MEMBRANE WALL MEMBERS CLOSING SAID AREA WITHIN SAID SURROUNDING SUPPORT FRAME MEMBERS AT EACH OF SUCH FACES, MEANS FOR COAXIALLY MOUNTING EACH PAIR OF SAID MEMBRANE WALL MEMBERS FROM SAID CURVED PORTIONS OF SAID SURROUNDING SUPPORT FRAME MEMBERS COMPLETELY AROUND THE PERIPHERY OF SAID AREA AND SEALING THE SPACE BETWEEN EACH PAIR OF SAID MEMBRANE WALL MEMBERS, AND MEANS FOR ADJUSTING THE PRESSURE WITHIN THE SPACE BETWEEN EACH PAIR OF SAID MEMBRANE WALL MEMBERS CAUSING SAID MEMBRANE WALL MEMBERS TO TENSION SAID SURROUNDING SUPPORT FRAME MEMBERS RADIALLY INWARD OF SAID AREA.   D R A W I N G

Farnsworth, 111

[45] Oct. 15, 1974 I 1 MODULAR VERTEX STRUCTURE [76] Inventor: Philo T.Farnsworth, III, PC. Box

251, Bolinas, Calif. 94924 [22] Filed: Jan. 9, 1970 [21] Appl. No.:1,583

[52] US. Cl 52/81, 52/DIG. 10, 52/73, 52/222 [51] Int. Cl E041) 5/43[58] Field of Search 52/79, 80,81, 73, 121, 52/DIG. 10; 292/296.61

[56] References Cited UNITED STATES PATENTS 3,633,325 l/-l972 Bartoli52/73 1,073,859 9/1913 Laskey 292/256.6l 3,127,699 4/1964 Wasserman52/81 3,153,235 10/1964 Chatelain 52/2 3,192,575 7/1965 Rosenan 52/171FOREIGN PATENTS OR APPLICATIONS 741,047 1966 Canada 52/81 1,088,671France 52/81 1,568,630 1969 France 52/73 45,677 1966 Germany 52/81843,529 1960 Great Britain 52/80 1,009,850 1965 Great Britain 52/81OTHER PUBLICATIONS Philosophical Transactions of the Royal Society ofLondon, Series A; Volume 246, p. 440, 441, 443 & 445, from UniformPolyhedra by Coxeter. Domebook 2, 1971, pages 9 and 10.

Primary Examiner-Frank L. Abbott Assistant Examiner-H. E. RaduazoAttorney, Agent, or Firm -Limbach, Limbach & Sutton 5 7 ABSTRACT Apolyhedral building structure is disclosed with formed side walls andmodular at the vertices thereof. The side walls can be in the form offrustoconical sections and the modular vertices can be in the form ofstructural members including first and second leg members lying alongedges that meet in a vertex and an arcuate portion extending betweenspaced apart portions of the leg members. The leg members can extendpartially or half-way to the next adjacent vertex. Frustoconicalsections can be located at and serve as the vertex portion of thepolyhedral structure. A building with a conical base portion projectingthrough one of the frustoconical sections can be utilized and modularpie-shaped floor sections positioned within the building structure overthe pedestal. The frustoconical sections can include one or moreevacuated or pressurized chambers formed by circular membranes thereinwhich provide integrity to the structure.

10 Claims, 15 Drawing Figures PATENIEBUBT 1 512m SHEEI 1 0f 6 IINVENTOR.PHILO T. FARNSWORTH H1 ATTORNEYS PATENTEB MT 1 51974 SHEEY BM 6 FIGBINVENTOR, PHILO T. FARNSWORTH I11 Pmmmm 3.841.039

SHEET 3 OF 6 FIG.5

INVENTOR.

PHILO T. FARNSWORTHJJI ATTORNEYS PAIENIEBWI l SIS SHEEI BF 6 FIG.7

INVENTOR. BYPHILU T.FARNSWORTH11I ATTORNHEYS SHEEI 5 OF 6 INVENTOR.PHILO IFARNSWORTHIII ATTORNEYS PAIENIEB w 3.841 .039

SHEET 6 0F 6 INVENTOR.

PHILO T. FARNSWORTH 111 ATTORNEYS MODULAR VERTEX STRUCTURE BACKGROUNDAND DESCRIPTION OF INVENTION I The present invention is directed to apolyhedral building structure, and. more particularly, to a modularstructure for low cost housing.

The need for low cost housing is an ever present need throughout theworld. It has long been recognized that the best way to provide low costhousing is to produce a functional structure that can easily beassembled on the site from a minimum number of different componentswhich are mass produced at a factory. To date, attempts to achieve thisresult have not been successful.

Broadly stated, the present invention, to be described in greater detailbelow, is directed to a polyhedral building structure with preformedside walls corresponding to the faces of a polyhedron and modular at theintersections of the side walls corresponding to the vertices of thepolyhedron.

In accordance with one aspect of the present invention, the side walls,as well as certain of the vertices as described below, are in the-formof frustoconical sections formed of a plurality of subassemblies.

In accordance with another aspect of the present invention, thesubassemblies join together to form the vertex of a member whereby astructure is provided which is modular at the vertex. These modularsubassemblies include first and second leg members lying along edgesthat meet in a vertex such that assembly of the appropriate number ofsaid subassemblies at a point will establish the vertex. With the legmembers equal in length to half the distance between vertices of apolyhedral structure, the entire structure can be formed by assemblingeach of the vertices fromthe appropriate number of said subassembliesand then connecting the adjacent vertices together to complete thepolyhedral construction.

In accordance with still another aspect of the present invention, thesubassemblies for forming modular vertices include arcuate portionsextending between spaced apart portions of the leg members whereby thearcuate portions form truncated conical sections when a plurality ofsaid subassemblies are joined together.

In accordance with still another aspect of the present invention, astructure is formed in accordance with the aspect of the precedingparagraph and wherein membranes, preferably circular, are supported inthe truncated conical sections to serve as wall members for thepolyhedral structure and at the same time act as structural support forthe individual truncated conical sections.

Where membranes are provided in the truncated conical'sections. aplurality of said membranes can be supported there and the pressure ofthe space between the membranes controlled with respect to atmosphericpressure to provide forces holding the modular members together and thuscontribute to the structural integrity of the polyhedral configuration.With membranes supported together at their periphery, pressurization ofthe space between the membranes establishes forces pulling the peripheryof the membranes inwardly to support the truncated conical section fromwhich the membranes aremounted. With the peripheries of a pair ofmembranes spaced apart along the surface of a truncated conical section,the

space between the membranes can be partially evacuhedral structure.

In accordance with still another aspect of the present invention,frustoconical sections can be located at and serve as the vertexportions of polyhedral structures, and where this aspect of the presentinvention is utilized in conjunction with frustoconical sections formingthe faces of the corresponding polyhedral structure, a buildingconstruction is provided with frustoconical sections of two differentdiameters.

Numerous construction features and advantages flow from use of modularmembers in accordance with the aspects of the invention described above.Accordingly, a building with a conical base portion projecting throughone of the frustoconical sections can be utilized and a modularpie-shaped floor section positioned within the building over thepedestal. A building of this nature can be manufactured in modular formin a factory utilizing mass production techniques and thebuildingquickly and easily assembled on the site with little or nopreparation of the building site or variation in the terrain of thebuilding site. I These and other features and advantages will becomemore apparent upon a perusal of thefollowing specification taken inconjunction with the accompanying drawings wherein similar characters ofreference refer to similar structures in each of the several views.

IN THE DRAWINGS: A f

FIG. I is a perspective view of a conic form of tetrahedron partiallybroken away and showing modular formation of the structure. at thevertices.

FIG. 2 is a view similar to FIG. I but of a conic form of hexahedromFIG. 3 is a view similar to FIG. 1 but of a conic form of octahedron.

FIG. 4 is a view similar to FIG. 1 but of a conic form of dodecahedron.

FIG. 5 is a view similar to FIG. 1 but of a conic form of icosohedronand partially broken away showing a building constructed in accordancewith the present invention.

FIG. 6 is a perspective view, partially exploded, illustrating structurefor formation of the structure illus-' trated in FIG. 5.

FIG. 7 is a perspective view of an alternativeembodiment of a portion ofthe structure :shown in FIG. 6.

FIG. 8 is an enlarged elevational sectional view of a portion'of thestructure shown in FIG. 5.

FIG. 9 is an enlarged section view of a portion of the structure shownin FIG. 8 delineated by line 99.

FIGS. 10 and 11 are viewssimila'r to FIG. 8 showing other embodiments ofthis invention.

FIG. l2is a schematic view illustrating one form of modularity of thepresent invention.

FIGS. 13 and 14 are views similar to FIG. 12 showing other modularityconstructions of the present invention.

FIG. 15 is a perspective view of still another embodiment of the presentinvention.

It will be appreciated from the foregoing and the detailed descriptionhereinafter that the present invention can be utilized in a great manyapplications. However, it is ideally suited as a building structure andcertain aspects particularly for low cost housing and therefore will bedescribed for illustrative purposes with respect thereto.

Referring now to the drawings with particular reference to FIGS. 1-5,there are shown polyhedral building structures of differentconfigurations embodying the present invention.

With particular reference to FIG. 1, there is shown a building structurein a conic form of tetrahedron which geometrically has four principalsides which meet along edges that intersectin four vertices. The conictetrahedral structure 10 has four frustoconical sections 11 which formthe faces of the tetrehedron and which, as shown, are built up fromstructural frame members 12 in modular form. Each of the structuralmembers 12 includes first and second leg members 13 and 14 which arejoined together at a vertex 16 of the tetrahedral structure 10 andextend along edges half way to an adjacent vertex 16 whereby threestructural members, one at each of the three vertices associated witheach frustoconical section, form the edges of the tetrahedron associatedwith each frustoconical section. In the structural member 12, an arcuateportion 15 defining one portion of the conical surface of thefrustoconical section 11 extends between leg members 13 and 14. Eachvertex 16 of the conic tetrehedral structure is thereby made up of threestructural members 12.

The wall portions 17 of the building structure can be formed in avariety of ways including disc members or membranes supported within thefrustoconical sections as described in greater detail below withreference to FIG. 8. As generally illustrated in FIG. 1, the wallportions can comprise a pair of circular or disc members 18 which arefixedly secured at their periphery to the arcuate portions of thestructural members 12 making up the frustoconical sections 11 andprovided with means, such as inflating valves, for pressurizing thespace between members 18. With pressure applied, the disc members pullradially inwardly on the frustoconical sections adding additionalsupport strength to the building structure. By selective inflation andselection of materials for the discs 18, the wall portions 17 of thefrustoconical sections can selectively pass light or sound and actuallyact as a lens structure.

The tetrahedral building can be assembled in any one of a number ofdifferent ways depending upon the materials selected for the structuralmembers 12. For example, depending upon their composition the structuralmembers 12 can be bolted,'welded. or glued together to form vertices l6and the free end of the leg members extending therefrom connected to legmembers from adjacent vertices by any convenient manner.

' Typically the strength of the building structure which structuresdescribed hereafter frustoconical sections making up a portion of thepolyhedra can be utilized.

of octahedron 24 having eight frustoconical sections 25 (FIG. 3), aconic form of dodecahedron 28 having twelve frustoconical sections 29(FIG. 4), and the conic form of icosohedron 30 having twenty frustoconical facial sections 31.

The conic form polyhedral structures illustrated in FIGS. 1-4 caninclude frustoconical minoror vertex sections at the vertices of thepolyhedron tangent to the frustoconical major or facial sectionsdescribed. For purposes of illustration, the conic form of icosohedronillustrated in FIG. 5 includes such frustoconical minor sections. Asillustrated there, the conic form of icosohedron includes twenty majorfrustoconical facial sections 31 corresponding to the twenty faces of anicosohedron and twleve minor frustoconical vertex sec tions 32 of adiameter different from the frustoconical facial sections 31 and locatedat the vertices of the corresponding icosohedron.

The shell structure of this conic form of polyhedron is modularized insuch a way as to build each vertex section 32 with five modules orstructural members 33 to form an 'assembly 34 defining a frustoconicalvertex section 32 and a portion of each of the five frustoconical facialsections 31 therearound. The complete conic icosohedral polyhedronapproximating a spherical structure can be formed with twleve suchvertex assemblies 34 or sixty identical modules in all.

As best seen in FIG. 6 each of the structural members 33 includes firstand second leg members 35 and 36, respectively, extending along edges ofthe corresponding icosohedral configuration, an outside arcuate portion37 extending between legs 35 and 36 and corresponding to a portion ofthe frustoconical facial section 31, and an inside arcuate portion 38extending between legs 35 and 36 preferably tangent to arcuate portions37 and corresponding to a portion of the frustoconical vertex section32.

Except for several of the vertical conical sections 31 and 32 which arereserved for egress, ventilation and mounting of the building, thefrustoconical sections 31 and 32 are closed by wall portions 41 and 42,respectively. As illustrated, each of these wall sections is formed by apair of disc members 43 and 44, such as of Mylar, coaxially mounted inthe frustoconical section at their periphery by a rim or bead 45 easilyinsertible into a special inflated closure molding 46. A valve member 47is provided for each pair of disc members 43 and 44 for pressuring thespace therebetween thereby giving the assembly a lens shape andshrinking the conical portions of the module members to which it ismounted together with a large pulling force.

Appropriate adjustment of the gas fill in the lens structure can renderthe building soundproof and metallization Y of the outside disc rendersthe lens transparent-to-translucent looking out of the structure butopaque looking in, as well as totally reflective looking both ways withregard to heat. This structure provides excellent vibrational damping.Where snow or wind load of a very large order is anticipated, lenssystems can be stacked with inter-lens pressure so as to load share theapplied forces.

The structural members 33 can include reinforcing wedges or be plasticfoam filled as illustrated in FIG. 6

and connection ropes or cables 49 can be provided along the arcuateportions 37 and 38 and/or leg members 35 and 36 for attaching thedifferent initially formed assemblies 34 together.

For the building structure, all utilities; drains, etc. enter throughand are cast in a concrete cone support pedestal 51 which supports andanchors the house through one of the frustoconical side or majorsections 31. This construction permits use of rough and hilly buildingsites, and numerous interesting division arrangements are possible.

In accordance with one embodiment of this invention, a primary floorplatform 52 is provided resting on the support pedestal 51 and extendingto the periphery of the polyhedral structure at that level. The floorplatform can be made up of a plurality of wedge-shaped members 53,containing the remaining electricalconnections and duct work, which canbe assembled on the support pedestal 51 and banded together by aperipheral holding cable 54. These elements 53 can include plug-inportions on their surface fo partitioning thereabove in a wide varietyof patterns. The interior plumbing tree, wiring, ducts, etc. arefabricated in-plant and mounted on fiberboard sections which plugtogether at the building site to become concrete forms for pedestal 51.

For assembly of the structure the support pedestal 51 is provided withthe frustoconical portion of one major or facial section 31 and fivestructural members 33 secured thereto to form-the first vertex assembly34. The connection cables 49 can be threaded on site or prethreaded andconnected to form twelve vertex assemblies 34'of five structural members33 each. The shell can then be erected vertex-by-vertex by the sametechnique. When the entire shell is up, the disc members 43 and 44forming the wall portions 41 and 42 can be inserted and pressurized inone rapid, almost tool-less operation. If the modules are not bonded atthe time of assembly, the entire structure can be disassembled andre-erected at a different location.

By way of example, one housing unit built in accordance with thisconstruction has a primary or platform diameter of 36-40 feet, anoverall diameter of45 feet, frustoconical major, facial or side sectionsof 13 feet in diameter, frustoconical minor or vertex sections of IOfeet in diameter, a length for the structural members 33 of about feetand a total weight for an empty house of 3-4 tons.

If it is desired to further modularize the structure shown in FIG. 6,the structural members 33 can be made up of left hand and right hand,half structural members 56 and 57 as illustrated in FIG. 7.

As illustrated in FIG. 9, the inflated closure molding 46 can include afirst substantially rigid retaining member 81 in the form of a beadextending around the frustoconical section 42 and provided with a groove82 in one surface thereof. Another support, partially flexible ridge 83provided with a groove 84 facing groove 82 is provided adjacentretaining member 81 but with a slot opening into the chamber defined bygrooves 82 and 83 adapted to receive the bead 45 at the periphery of thediscs 43 and 44. The ridge 83 includes internally thereof an inflatablechamber 85 which forces the ridge 83 against retaining member 81 toclamp the bead 45 in the grooves 82 and 84.

While FIG. 8 illustrated the manner in which the discs 43 and 44 can bepositioned in the frustoconical section and the space 40 therebetweenpressurized to hold the portions of the frustoconical sections together,other constructions of the disc members are possible. For example, withreference to FIG. 10, the discs 43' and 44 can be mounted at spacedapart locations adjacent the larger and smaller ends of thefrustoconical section 42. Then the space 40 between the discs 43' and44' can be partially evacuated through a valve member 47' whereby thestretching force on the disc members due to the difference in pressureon opposite sides thereof will hold the portions of the conical sectiontogether and serve to support the integrity of the overall structure.

Referring now to FIG. 11, there is shown still another embodiment of thepresent invention using a plurality of discs wherein a pair of discs 43aand 44a are mounted along a common line on the surface of thefrustoconical section 42" and a third disc 44b mounted along a linespaced from the, line for mounting discs 43a and 43b. The space 40abetween discs 43a and 44a can be pressurized while the space 40b betweendiscs 44a and 44b can be partiallyevacuated to give both desiredrigidity to the overall structure and accomplish multiple functions withthe different discs and spaces be tween the'discs for producing desiredthermal, acoustic and optical characteristics for the structure formedof a plurality of these frustoconical sections.

It will be appreciated that frustoconical sections forming either thesides-of a polyhedron orlocated at the vertices of the polyhedron can,where desired, be subdivided into other frustoconical sections ofappropriate dimension.

As will be appreciated from the description above, one aspect of thepresent invention for providing an easily assembled structure from aplurality of identical modules is the provision of a polyhedralstructure that is modular at the vertex. This concept is applicable notonly to the conic forms of polyhedra, such as those illustrated in FIGS.1-5, but also to regular polyhedra. By way of example, reference is nowmade'to, FIG. 12 showing the edge members of a dodecahedron formed bysupport members 62 which include edge portions 63 and 64'extending froma vertex 65 of the structure along two edges to two of the adjacentvertices. By assembling the same number of these support members 62 asthere are edges meeting at the vertex 65, the vertex of the polyhedron61 is established. Next, by assembling the required number of verticestogether, the entire polyhedron is formed. While it is preferred thateach of the leg members 63 and 64 extend half way from the vertex 65 toan adjacent vertex for joinder with leg members from such adjacentvertex, these leg members can be of a different length and the shorteror longer leg members 63 and 64 connected by connection members.

The transformation of the assembly modular members shown in FIG. 12 forthe formation of a conic form of polyhedron is illustrated in FIG. 13wherein an arcuate portion 68, such as the arcuate portions in themodule of preceding figures, extends between leg members 63 and 64.Naturally, advantages of the conic form of pol'yhedra such as strengthcan be sacrificed and hybrid structures, such as oval rather thancircular configurations, utilized. As illustrated in FIG. 14, apolyhedral structure in accordance with the present invention can beformed utilizing oval rather than conic portions for the modular membersand wherein left and right hand modules 71 and 72 are used.

Obviously certain modifications in the structures and structural membersdescribed above can be made within the scope of the present invention.For example, while the invention has been illustrated in FIGS. lwithrespect to regular polyhedra, other geometrical shapes can be used suchas nonregular structures or partial nonregular structures.

A structure can be formed of different dimensioned modular vertexelements such as the example shown in FIG. 15. As shown there a rhombicdodecahedron can be formed with elliptical facial or side sectionswherein modular elements 81 form the longer arcuate sides of a conicelliptical section for the rhombic dodecahedron vertices formed by threeedges and modular elements 82 form the shorter arcuate sides of theconic elliptical section for the rhombic dodecahedron vertices formed byfour edges.

Even though there is one origin or geometric center of the structureillustrated and described thus far, hybrid structures with more than oneorigin are possible constructions of the modular vertex system.Similarly, considering the distance from the origin or origins to thearcuate portions of the frustoconical sections as the radius, a singlestructure can be formed with conic section of different radii or varyingradii such as shown in FIG. 15.

What is claimed is:

1. A polyhedral structure having a plurality of vertices and a pluralityof edges meeting at each of the vertices and defining the faces of thepolyhedral structure comprising:

a plurality of support frame members defining the edges which define atleast certain faces of thepolyhedral structure, each of said supportframe members having at least one leg member of a pair of leg membersextending at least part way along edges defining such faces and at leastone curved portion defining an arc of a substantially circular areacentered in the face of the I polyhedral structure defined by suchedges, the plurality of support frame members at each face joinedtogether with the curved portions thereof completely surrounding saidsubstantially circular area thereof, I at least a pair of substantiallycircular membrane wall members closing said area within said surroundingsupport frame members at each of such faces, means for coaxiallymounting each pair of said membrane wall members from said curvedportions of said surrounding support frame members completely around theperiphery of said area and sealing the space between each pair of saidmembrane wall members, and v means for adjusting the pressure within thespace between each pair of said membrane wall members causing saidmembrane wall members to tension said surrounding support frame membersradially inward of said area. 2. The structure of claim '1 wherein thespace between the membrane members of at least certain pairs ofmembrane'wall members is evacuated to be below atmospheric pressure.

3. The structure of claim 1 wherein the space between the membranemembers of at least certain pairs of membrane wall members ispressurized to be above atmospheric pressure.

4. The polyhedral structure of claim 1 wherein said membrane wallmembers are plastic and at least one member of each pair is partiallymetalized.

5. The structure of claim 1 wherein at least certain membrane wallmember pairs include a third membrane wall member, the space between thepair of membrane wall members being evacuated to be below atmosphericpressure and the space between said third membrane wall member and oneof said pair of membrane wall members is pressurized to be aboveatmospheric pressure.

6. A structure comprising:

means defining a plurality of hollow frusto, substantially conicalsections joined together with adjacent sections tangent to one anotherand the axes of all said sections intersecting in a point,

said section-defining means including a plurality of structural framemembers,

each of said structural frame members having at least one leg member ofa pair of leg members extending at least part way along tangent linesbetween sections and at least one curved portion defining an arc of asaid conical section,

the plurality of frame members of each section joined together with thecurved portions thereof completely surrounding said conical sections,

at least a pair of circular membrane wall members closing each conicalsection,

means for coaxially mounting each pair of said membrane wall membersfrom said curved portions of said surrounding frame members completelyaround the periphery of said conical section and sealing the spacebetween each pair of said membrane wall members, and

means for adjusting the pressure within the space between each pair ofsaid membrane wall members causing said membrane wall members to tensionsaid surrounding frame members radially inwardly of said conicalsections.

7. The structure of claim 6 wherein the space between the membranemembers of at least certain pairs of membrane wall members is evacuatedto be below atmospheric pressure.

8. The structure of claim 6 wherein the space between the membranemembers of at least certain pairs of membrane wall members ispressurized to be above atmospheric pressure;

9. The structure of claim 6 wherein said membrane wall members areplastic and at least one member of each pair is partially metalized.

10. The structure of claim 6 wherein at least certain membrane wallmember pairs include a third membrane wall member, the space between thepair of membrane wall members being evacuated to be below atmosphericpressure and the space between said third membrane wall member and oneof said pair of membrane wall members is pressurized to be aboveatmospheric pressure.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent 3,841,039Dated October 15, 1974 Inventor) Philo T. Farnsworth II I It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

The term of this patent subsequent to April 15, 1989, has beendisclaixned.

Signed and sealed this 13th day of May 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officerand Trademarks FORM PO-\050(10-69) us covznnusnr Pmu'nuc orncs: 93 o

